Cut the chicken breasts in half, lengthwise to create 4 thin-cut breasts. Place the chicken breasts into a large mixing bowl. Add the pesto, garlic powder, onion powder, salt, and pepper to the bowl and toss to coat the chicken.
Place a large skillet over medium heat. (I like to use cast iron.) Once the skillet is hot, add the olive oil and sear the chicken for 3-4 minutes per side until it's cooked through (with an internal temperature of 160 degrees F).
Sandwiches
To assemble the sandwiches, lay the rolls cut side down onto a sheet tray. Brush the tops and bottoms of the rolls with olive oil. (It might seem like too much olive oil, but use it all.)
Flip the rolls over so they are cut side up. Spread the mayonnaise evenly on both sides of each roll, and then spread the pesto over the mayonnaise.
On the bottom side of each roll, place one piece of pesto chicken. Then add two slices of mozzarella and one slice of tomato on top of the chicken. Sprinkle black pepper on top of the tomatoes, if desired. Place the tops of the rolls on the sandwiches.
Preheat your panini press. Add as many sandwiches to the press as will fit. Cook for 5-7 minutes to your desired toastiness making sure the cheese is melted. The sandwiches are tall, so you may need to gradually press them down as they cook.
Transfer to a plate and serve immediately. I like to cut the sandwiches in half after plating to make then a little easier to eat.
Notes
To cook the sandwiches without the panini press:
Prepare the pesto chicken as directed. Wipe out the cast iron (or oven-safe) skillet and place it back over medium heat. Add 2 tablespoons of olive oil to the pan.
Toast the rolls cut side down in the hot oil until golden, then flip them over. Add the mayonnaise, pesto, chicken, mozzarella, and tomato slices as directed. Place the tops of the rolls over the sandwich filling.
Put the skillet into a 350 degrees F oven and cook until the cheese has melted and the sandwiches are warmed through, about 10 minutes.
*Alternatively, if you don’t have an oven-safe skillet, you can place the prepared sandwiches onto a baking sheet and then place them in the oven to bake.